1. Field of the Invention
The present invention relates to construction of parafoils and parachutes. More particularly, it relates to use of a composite, non-woven material for parafoils and parachutes and methods of reinforcing such devices using such material as a reinforcing tape.
2. Background
Parachutes, both decelerator type and ram-air, gliding wing type, are typically constructed from rip-stop nylon fabric. Rip-stop nylon is a square woven fabric, with the warp and weft fibers being positioned at 90 degrees to each other. The material is then typically treated with a silicone based chemical and calanderized to fill in the pores of the fabric to reduce its porosity and control air flow through the fabric. The treatment causes the fabric to become slick and non-stick.
The material as used in parachutes, must have various qualities, such as:                good tear strength (even after many hours exposed to Ultra Violet rays (UV);        low permeability to keep the cells pressurized;        light weight for better inflation; and        reduced packing volume.        
Rip-stop nylon has advantages in weight, tear strength and longevity. The chemical make up of coatings and how they are applied to the fabric also affect the qualities of the final product.
Parachutes are designed to have a specific form during flight and is constructed from various panels which are shaped and put together to achieve the desired form. However, during flight, the fabric is subjected to complex mechanical and aerodynamics stresses which stress the fabric along the direction of its laid fibers, and in various patterns at a bias to the weave. As such, the actual shape of the assembled panels and the resulting inflated structure during flight, distort away from the desired modeled shape.
To combat this problem, the construction of a parafoil or parachute generally includes heavy narrow woven fabric tapes (or webbing) that is stitched into the structure to restrain the fabric panels into a shape closer to that modeled. However, the inclusion of reinforcing tape in the design adds packing volume and construction complexity.
Other problems with woven fabric reinforcing tapes include: inherent stretchability in various directions (the degree of stretch depends on the fiber, type of weave, and the directions of the stresses) and shrinking from exposure to water and abrasion from absorbed particles and mildew.
The construction of parafoils and parachutes with rip-stop nylon panels and reinforcing tapes is also subject to construction tolerance errors by the nature of the sewing construction process. Specifically, due to the slick coating material, and the low tolerances in the design of parachute, highly skilled workers are required to construct a parachute. Even with highly skilled labor, the parachute is subject to inaccuracies during construction. For example, since the seams are tensioned by the sewing process and shrink, the accuracy of the constructed shape with respect to the design is limited.
For example, a common seam in a parachute involves three overlaying fabric panel edges plus a reinforcing tape. The reinforcing tape is rolled over and stitched over the entire length with a double needle lockstitch. It is extremely difficult to hold tolerances of several millimeters on match marks during this sewing process. Moreover, accumulative errors along a span of an average personnel parachute can amount to several inches. Thus, even before additional distortions are created due to stresses on the fabric, the parachute shape may vary from the design.
It is also difficult to test parachute designs or to obtain accurate data relating to parachute performance during flight, such as pressure distributions, air flows, and material shape, movement and stress. Obtaining such information has been attempted using wind tunnels. However, only two wind tunnels exist in the United States which are large enough for small to medium sized parachutes. Also, wind tunnels cannot provide accurate information regarding actual flights. The conditions in an wind tunnel are perfect and constant and do not necessarily reflect conditions during flight.